A mobile communication system, a third generation asynchronous mobile communication system WCDMA (Wideband CDMA), ensures high service quality and high-speed mobility. Since an enormous investment is required to realize the system, it is not possible to provide a service broadly. Thus, currently, the synchronous mobile communication system (CDMA mobile communication system) that is called second generation or second and half generation coexists.
With the technical development of such mobile communication network, a mobile communication terminal (Multi-Mode Multi-Band Terminal; DBDM mobile communication terminal), which is available for both the synchronous system and the asynchronous system, is developing. By using the mobile communication terminal, different ways of service can be provided in the asynchronous system and in the synchronous system.
In the mobile communication system, when a power source is applied to the mobile communication terminal, the mobile communication terminal selects one frequency band among a plurality of available channels and uses the service. In the synchronous mobile communication system, since the mobile communication terminal selects a certain frequency band by using its own number, it is very rare for the calls to be concentrated into a certain channel.
However, in the asynchronous mobile communication system, since the mobile communication terminal attempts calls to a channel of which the intensity of the receiving signal is higher than others, the distribution of calls among the channels may not be uniform.
Specifically, in case of the synchronous mobile communication system, the primary channel and the secondary channel are stored in the NAM (Number Assignment Module) of a mobile communication terminal. Thereafter, if the power source is applied to the mobile communication terminal, calls are preferentially attempted through a basic channel. In addition to the basic channel and the second channel, a mobile communication terminal number, a network provider segment number, a connection exchanger number, etc., which are required to process calls, are stored in the NAM. At the time of opening the mobile communication terminal, equivalent values are input by an operator. Herein, when a mobile communication terminal is connected to the mobile communication network, the basic channel information and the second channel information are assigned based on designated criteria so as not to be concentrated into a certain channel. According to this process, each mobile communication terminal can always use services through an identical channel in the synchronous mobile communication system.
On the other hand, since the asynchronous mobile communication system has fewer subscribers than the current synchronous mobile communication system, the connection channel is not differentiated per subscribers. In stead, it is connected to the channel having most superior receiving sensitivity when using services.
However, if a number of subscribers, who use the asynchronous mobile communication system, try calls at the same time, the waste of wireless resource gets severe and service quality becomes deteriorated.
FIG. 1 is a conceptual diagram for explaining a channel allocation method for a general asynchronous mobile communication system.
As illustrated, a plurality of mobile communication terminals (10-1˜10-n) are connected to the node B/wireless network controller (RNC)(20), and a mobile communication terminal (10-m) is connected to the node B/RNC (20) through a channel 2 (FA2). The mobile communication terminals (10-1˜10-n, 10-m) do not try a connection after being assigned with channels to connect with each node, but use services by selecting a channel having the most superior receiving sensitivity (FA1 in FIG. 1) at the initial stage of being applied with power source.
In FIG. 1, EMS (Element Management System) is an operator system to manage a wireless environment in the mobile communication system.